Rinse the glutinous rice in a fine mesh sieve under cold running water until the water runs clear. Soak overnight.

Drain the rice and steam in a bamboo steamer lined with parchment paper for 20-25 minutes until translucent and tender.

Heat 1 cup of coconut milk in a saucepan, add granulated sugar and sea salt, and stir until dissolved.

Stir in the ube halaya and optional ube extract until well combined.

Add the steamed rice to the coconut-ube mixture and stir until well-coated; cook on low for 4 minutes.

Let the mixture cool in the pan for about 5 minutes.

For the coconut sauce, combine another 1/2 cup of coconut milk with sugar, bring to boil, then mix in the cornstarch slurry until thickened.

Peel and slice the mangoes into thin strips.

To serve, mound sticky rice on a plate, arrange mango slices, drizzle coconut sauce, and sprinkle toasted coconut on top.